Nuttx is a real-time embedded operating system (RTOS). It has a small footprint that is usable in micro-controller environments. It is fully scalable from tiny (8-bit) to moderate embedded (32-bit) systems. It also aims to be fully compliant to standards, to be fully real time, and to be totally open.
The Epoch Init System is an init system for Linux designed with ease of configuration and non-intrusiveness in mind. It has no external dependencies besides libc and pthreads on a Linux 2.6+ system, though a working /bin/sh is suggested. It's suitable for large and small Linux distributions, but was designed with a focus on smaller Linux systems. It's features include a log system capable of recording boot events before the filesystem is made writable, ASCII runlevels, a convenient, single configuration file setup, automatic hostname setting at boot, automatic virtual filesystem mounting (think /proc), PID file support, stuck job killing during bootup and shutdown, integrated color greeting banner support, and automatic service restart support, to keep vital services running at all times.
Gpart is a small tool which tries to guess which partitions are on a PC harddisk in case the primary partition table was damaged. It works by scanning through the device (or file) given on the commandline on a sector basis. Each guessing module is asked if it thinks a filesystem it knows about could start at a given sector. Several filesystem guessing modules are built in, and others can be added dynamically.
samhain is a daemon that can check file integrity, search the file tree for SUID files, and detect kernel module rootkits (Linux only). It can be used either standalone or as a client/server system for centralized monitoring, with strong (192-bit AES) encryption for client/server connections and the option to store databases and configuration files on the server. For tamper resistance, it supports signed database/configuration files and signed reports/audit logs. It has been tested on Linux, FreeBSD, Solaris, AIX, HP-UX, and Unixware.
Rspamd is an anti-spam system designed to work faster than SpamAssassin by using the event model and various optimizations. Its most important features include regexp and Lua rules for filtering different parts of messages, a number of built-in functions for analyzing messages, fuzzy hash support, SURBL filters, email and character table support, a control interface for remote managing and stats gathering, a Lua plugin system, statistics support (OSB/Bayes), and an AJAX-based Web interface.
Jaro Mail is an integrated suite of interoperable tools for GNU/Linux and Apple/OS X to manage email communication in a private way, without relying on online services (in fact, encouraging users to store email locally). It mainly features a system for mailinglist filtering, address-book integrated whitelisting, and long-term email storage and archiving with functions for fast search and usage statistics. It makes internal use of customized versions of popular Unix tools like Mutt, Fetchmail, Procmail, Mairix, and Msmtp.